Rotation mechanism for laser emitter

ABSTRACT

A rotation mechanism for mounting and rotatably supporting a laser emitter thereon includes a casing including a bottom wall and a side wall connected to the bottom wall, said casing defining therein a receiving space. A plurality of rotation rings are arranged as being layered with each other in the receiving space of the casing. The rotation rings include an uppermost rotation ring in the form of a manual coarse rotation ring that is directly connected to the laser emitter so as to support the laser emitter, for manually rotating the laser emitter to achieve a coarse angular positioning thereof, an automatic coarse rotation ring for rotating the laser emitter at a relatively high speed together with the rotation ring thereon, a manual fine rotation ring for slightly rotating the laser emitter manually together with the rotation ring thereon, and an automatic fine rotation ring for rotating the laser emitter at a relatively low speed, together with the rotation ring thereon. The automatic rotation rings are each provided with a driving means that is arranged on the rotation ring immediately below the relevant rotation ring.

TECHNICAL FIELD

The present invention relates to a rotation mechanism for a laseremitter, which can be suitably used for marking purpose in constructionor civil engineering sites, and which is designed to rapidly andaccurately rotate the laser emitter to a position corresponding to thedirection in which laser is to be emitted.

BACKGROUND ART

There is known a laser emitter for emitting and displaying a laser lineon a surface of a wall, ceiling or floor, which includes a rotationmechanism incorporated into the lower end region of the emitter mainbody, such that the laser line generated can be radiated over an angularrange of 360°. In this instance, when the laser emitter has beeninstalled, the marking is performed after manually operating therotation mechanism so as to cause a coarse rotation of the emitter mainbody, by accurately aligning the laser line to the target site by a fineadjusting movement (cf. Patent Document 1: JP9-166436A).

This type of laser emitter requires an extremely delicate and preciseadjustment when the laser line is to be manually focused to the targetsite by an operator, in particular when the laser line is generated soas to form a vertical line. Such an adjustment is a heavy burden to theoperator. It is needless to say that the adjustment becomes less easywhen the distance between the laser emitter and the light receivingelement increases, even when a fine adjustment mechanism is provided.

In order to overcome such a problem, there is also known a laser emitterthat can be rotated by a remote control and stopped when the laser lineemitted from the laser emitter is detected by a light receiving elementthat has been previously arranged at the target site (cf. PatentDocument 2: JP2000-230828A, and Patent Document 3: JP2001-191271A).

While the laser emitter of remote control type as mentioned above allowssimplification of the manual operation and proved to be an effectivemeasure for reducing the time required for marking, there is suchdisadvantage that the system becomes large due to the requirement for adriving source for the laser emitter.

Besides, while a coarse positioning adjustment is generally performed bymanually rotating the emitter main body, particularly in the case of thelaser emitter of remote control type, the driving system tends to besubjected to an excessive load when the emitter main body is manuallyrotated, which may cause mechanical failures.

DISCLOSURE OF THE INVENTION Task to be Solved by the Invention

It is an object of the present invention to provide a rotationmechanism, which allows a rapid and accurate focusing of the laser lineemitted from the laser emitter, which is not subjected to an excessiveload that may lead to mechanical failures, even when rotated manually,and which is compact in structure.

Means for Solving the Task

According to the present invention, there is provided a rotationmechanism for mounting and rotatably supporting a laser emitter thereon,said rotary mechanism comprising:

-   a casing including a bottom wall and a side wall connected to the    bottom wall, said casing defining therein a receiving space; and-   a plurality of rotary rings that are arranged as being layered with    each other in the receiving space of the casing;-   said plurality of rotation rings comprising: an uppermost rotary    ring in the form of a manual coarse rotation ring that is directly    connected to the laser emitter so as to support the laser emitter,    for manually rotating the laser emitter to achieve a coarse angular    positioning thereof; an automatic coarse rotation ring for rotating    the laser emitter at a relatively high speed together with the    rotation ring thereon; a manual line rotation ring for slightly    rotating the laser emitter manually together with the rotation ring    thereon; and an automatic fine rotation ring for rotating the laser    emitter at a relatively low speed, together with the rotation ring    thereon; and-   the automatic coarse rotation ring and the automatic fine rotation    ring each having driving means arranged on the rotation ring    immediately below the relevant rotation ring.

In the rotation mechanism constructed as above, it is preferred that thedriving means for the automatic coarse rotation ring comprises a DCmotor for allowing a high speed rotation, and the driving means for theautomatic fine rotation ring comprises a stepping motor for allowing alow speed rotation.

The side wall of the casing may have window openings that are spacedfrom each other at an angular distance of approximately 90°, wherein thewindow openings are each provided with at least two sensors adapted toreceive control signals for the driving means of the automatic coarserotation ring and the driving means of the automatic fine rotation ring,the at least two sensors of each window opening being oriented inmutually different directions.

A highly accurate positioning can be achieved if the monitoring timeafter completion of tracking is set to at least 3 seconds.

According to the present invention, there may be arranged powertransmission means between the automatic fine rotation ring and thedriving means thereof, wherein the power transmission means comprises: aguide pin integral with, and projecting from an outer periphery of theautomatic fine rotation ring; a guide member having catch portionsengaged with the guide pin from both sides in a direction in which theautomatic fine rotation ring is rotated; a screw rod for holding theguide member in a threaded engagement therewith, and adapted to berotated by the driving means so as to cause a sliding movement of theguide member back and forth along the longitudinal axis of the screwrod; and a pair of interrupters for performing a recovery control bydetecting forward and rearward sliding limits of the guide member andcausing, when it has been detected that the sliding limit has beenreached, the automatic fine rotation ring and the automatic coarserotation ring to be rotated in a clockwise or counterclockwise mannerwhenever necessary, so as to position the laser line with a convergentpoint.

Effects of the Invention

The rotation mechanism for a laser emitter according to the presentinvention has a layered structure wherein the laser emitter is directlyconnected to the uppermost rotary ring in the form of a manual coarserotation ring, and the automatic coarse rotation ring and the automaticfine rotation rings are arranged below the manual coarse rotation ring.Therefore, a manual operating force is applied only to the manualrotation rings, without being influenced by the weight of the drivingsystem or electric power supply. In other words, the manual rotation canbe performed lightly, without applying any load that may cause failureof the automatic rotation rings.

According to the present invention, furthermore, since the driving meansfor the automatic rotation rings are each arranged on the relevantrotation ring on the lower side, the provision of a dedicated space forthe driving means is unnecessary, thereby readily realizing a compactarrangement of the rotation mechanism.

In practical application, the laser emitter should be rotated at a highspeed when the laser line is situated remote from the position to bemarked, whereas the laser emitter should be rotated at a low speed whenthe laser line is situated close to the position to be marked. However,when the driving means comprises a DC motor which is suitable for a highspeed rotation, as a general matter, it is not easy to precisely stopthe DC motor at a predetermined angular position. Thus, the rotationspeed of the DC motor must be controlled by adjusting the PWM signal,for example, thereby requiring a complex setting and complicatedstructure. In contrast, when a stepping motor is used, in order toprecisely stop the motor at the position to be marked, it would beinevitable to minimize the amount of angular rotation of the motor perunit step. However, when the stepping motor is rotated with a minimizedamount of angular rotation, there arises a disadvantageous problem thata longer time is required to complete the positioning of the laser line.When, as in a preferred embodiment of the present invention, a DC motorand a stepping motor are used in combination, a precise positioning ofthe laser line at the position to be marked can be performed within ashort time, by the DC motor for the coarse adjustment and the steppingmotor for the stepping motor.

When the laser line is positioned to the center (i.e., the convergentpoint) of the light receiving sensor of the receiver by driving theautomatic fine rotation ring by means of the stepping motor, because thestepping motor drives the automatic fine rotation ring in a stepwisemanner with a predetermined stepping angle, there may be instanceswherein the laser line passes over the convergent point. In such a case,because the laser line is continuously rotated in a direction away fromthe convergent point, the positioning cannot be performed quickly. Sucha potential problem can be eliminated by a preferred embodiment of thepresent invention, wherein power transmission means is arranged betweenthe automatic fine rotation ring and the driving means thereof, andprovided with interrupters which performs a recovery control bydetecting the sliding limits of a guide member for controlling therotation of the automatic fine rotation ring and causing, when it hasbeen detected that the sliding limit has been reached, the automaticfine rotation ring and the automatic coarse rotation ring to berepeatedly rotated in a clockwise or counterclockwise manner whenevernecessary, so as to position the laser line with a convergent point.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described below in further detail, withreference to the accompanying drawings, wherein:

FIG. 1 shows the arrangement of a laser emitter and a receiver, whereinthe laser emitter is equipped with the rotation mechanism according tothe present invention;

FIG. 2 is an exploded perspective view of the rotation mechanism;

FIG. 3 is a diagram showing the structure of the receiver;

FIG. 4 is a block diagram of the rotation mechanism;

FIG. 5 is a plan view showing the arrangement of the sensors;

FIG. 6 is a detailed view of a knob portion;

FIG. 7 is a schematic view showing the arrangement of an emitter foremitting a laser line for marking a floor surface;

FIG. 8 is a schematic view showing the operation of the emitter of FIG.7:

FIG. 9 is a schematic view showing another example of the receiver;

FIG. 10 is a perspective view showing the detail of the stepping motorunit in the rotation mechanism according to the present invention;

FIGS. 11( a) and 11(b) are time charts showing the rotation of theautomatic coarse rotation ring and the automatic fine rotation ring,respectively;

FIG. 12 is a schematic view showing one example of the interrupters; and

FIG. 13 is a schematic view showing another example of the interrupters.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIG. 1, there is shown the arrangement of an automatictracking-type laser emitter and a receiver for receiving a laser line(e.g., a vertical line, as in the illustrated embodiment) which isgenerated by the emitter, wherein the laser emitter is equipped with therotation mechanism according to the present invention. The explodedperspective view of the rotation mechanism is shown in FIG. 2.

In the drawings, reference numeral 1 denotes the laser emitter,reference numeral 2 denotes a rotation mechanism for rotatablysupporting the laser emitter 1, reference numeral 3 denotes a tripodprovided at the bottom portion of a casing 2 a of the rotation mechanism2, reference numeral 4 denotes a knob portion for causing a coarserotation of a manual coarse rotation ring of the rotation mechanism, andreference numeral 5 denotes a receiver (light receiving unit) forreceiving the laser generated by the laser emitter 1.

The casing 2 a of the rotation mechanism 2 includes, as shown in FIG. 2,the bottom portion 2 a ₁, a side wall 2 a ₂ connected to the bottomportion 2 a ₁, and a bottom cover 2 a ₃, and defines a receiving space Ktherein.

Within the receiving space K, there are sequentially arranged in alayered manner, as seen from the upper side, a manual coarse rotationring 2 b directly connected to the laser emitter 1 for supporting thelaser emitter 1 and manually rotating it to achieve a coarsepositioning, an automatic coarse rotation ring 2 c for rotating thelaser emitter at a relatively high speed, an automatic fine rotationring 2 d for rotating the laser emitter 1 at a relatively low speed toachieve a fine positioning, and a manual fine rotation ring 2 e formanually rotating the laser emitter 1 to achieve a fine positioning.These rotation rings are rotatable about a shaft p that is integrallyprovided on the bottom portion 2 a ₁ of the casing 2 a.

Reference numeral 6 denotes a fitting for securing the laser emitter 1to the manual coarse rotation ring 2 b and preventing withdrawalthereof, reference numeral 7 denotes a helical gear connected to theautomatic coarse rotation ring 2 c, and reference numeral 8 denotes a DCmotor unit including a reduction gear mechanism, for driving theautomatic coarse rotation ring 2 c into rotation, through the helicalgear 7. The DC motor unit 8 is designed to have a reduction ratiosuitable for coarsely driving the automatic coarse rotation ring 2 c ata high speed, and fixedly arranged on the automatic fine rotation ring 2d that is situated immediately below the automatic coarse rotation ring2 c.

Reference numeral 9 denotes a stepping motor unit including a powertransmission mechanism, for driving the manual fine rotation ring 2 cinto rotation. The stepping motor unit 9 is designed to precisely rotatethe automatic fine rotation ring 2 d, and fixedly arranged on the manualfine rotation ring 2 e that is situated immediately below the automaticfine rotation ring 2 d.

Reference numeral 10 denotes a circuit board arranged inside of thebottom cover 2 a ₃ and incorporating a driver circuit for driving therotation mechanism 2 so as to rotate the laser emitter 1, referencenumeral 11 denotes notches formed in the bottom cover 2 a 3 at anangular interval of 90° to define window openings, reference numeral 12denotes filters for shielding the respective notches 11, and referencenumerals 13 a to 13 d denotes sensors arranged on the circuit board 10and directed toward outside through the filters 12 in the notches 11.These sensors 13 a to 13 d constitute a signal reception means forreceiving signals transmitted from the receiver 5 so that, in responseto the received signals, the DC motor unit 8 or the stepping motor unit9 is operated to rotate the automatic coarse rotation ring 2 c or theautomatic fine rotation ring 2 d, thereby to move the laser line to adesired location.

In the arrangement shown in FIG. 1, the laser emitter 1 is illustratedas generating a single vertical laser line L. However, the laser emitter1 may be designed so as to generate a plurality of laser lines or alaser beam for marking a floor surface. The laser emitter 1 is used incombination with the receiver 5 for receiving the laser line generatedfrom the laser emitter 1.

In the embodiment of the receiver 5 as shown in FIG. 3, the lightreceiving sensor portion is formed by light receiving elements 5 a, 5 bwhich are arranged on the left and right sides. The laser emitter 1 isrotated by the rotation mechanism 2 and thereby adjusted or positionedsuch that the laser line L coincides with the center portion O(convergent point) of the light receiving sensor portion. Depending uponthe situation, there may be instances wherein the position of thereceiver itself is changed.

When the laser line L emitted toward the light receiving sensor portionof the receiver 5 is incident on the sensor 5 a on the right side, thetransmitter 14 of the receiver 5 transmits a command signal to thesignal reception means of the rotation mechanism 2 so that the laserline is moved toward left and positioned to the center portion O of thelight receiving sensor portion. On the contrary, when the laser line Lemitted toward the light receiving sensor portion of the receiver 5 isincident on the sensor 5 b on the left side, the transmitter 14 of thereceiver 5 transmits a command signal to the signal reception means ofthe rotation mechanism 2 so that the laser line is moved toward rightand positioned to the center portion O of the light receiving sensorportion.

The optical signals obtained by the sensors 5 a, 5 b are subjected tofiltration by filter amplifiers 15 a, 15 b to have a required frequencyband only, signal conversion by rectifiers 16 a, 16 b, and signalprocessing and by a microcomputer 17. On this occasion, the outputsignal of an acceleration sensor 18 is also supplied to themicrocomputer 18 to provide current position information, based on whichthe sequence of the signals from the sensors 5 a, 5 b are changed orreturned.

The receiver 5 includes LEDs 19, 20, 21 and acoustic buzzer, etc, fordisplaying the status of light reception, and other switches 22 to 24.

One embodiment of the rotation mechanism according to the presentinvention is shown in FIG. 4, wherein the signals transmitted from thetransmitter 14 of the receiver 5 are received by the sensors 13 a to 13d of the rotation mechanism 2 and supplied, through an optoelectronicconversion circuit 25, to a microcomputer 26 for signal processing so asto operate driver circuits 27, 28 to drive the DC motor unit 8 and thestepping motor unit 9 and thereby rotate the automatic coarse rotationring 2 c or automatic fine rotation ring 2 d. if necessary.

FIG. 5 is a plan view showing the arrangement of the sensors 13 a to 13d, and FIG. 6 is a detailed view of the knob portion 4 for causing afine movement of the manual fine rotation ring 2 e.

When the sensors 13 a to 15 d are arranged as shown in FIG. 5, it ispossible to positively receive the signals from the receiver 5. However,the present invention is not limited to such a specific arrangement, andit is possible to adopt various types of arrangement.

One example of the structure of the knob portion 4 is as follows. Asshown in FIG. 6, the manual fine rotation ring 2 f is provided with aprojection t, which is clamped from both sides between screw rods 4 a, 4b. One of these screw rods, i.e., the screw rod 4 b, is illustrated ashaving a tip end portion that is resiliently biased by a spring s. It ispossible to cause a fine movement of the manual fine rotation ring 2 e,by suitably rotating the screw rod 4 a in a clockwise orcounterclockwise manner. A similar mechanism can be applied also to theautomatic fine rotation ring 2 d, except the motor and the gears of thepower transmission system. However, the present invention is not limitedto such a specific arrangement of the knob portion 4.

In the laser emitter capable of generating a laser beam spot for markinga floor surface, as schematically shown in FIG. 7, the shaft p of therotation mechanism 2 has a bore 29 extending therethrough, so as toallow the passage of the laser beam for marking the floor surface.

In such a structure of the laser emitter 1, as schematically shown inFIG. 8, there may be provided within the rotation mechanism 2, aninfrared signal transmission portion 30 adjacent to the bore 29, and aninfrared signal reception portion 30 at the exit opening of the laseremitter 1. In this instance, the signal obtained through the filter 12of the rotation mechanism 2 is transmitted from the transmission portion30 toward the laser emitter 1, i.e., toward the reception portion 31while reflecting inside or the bore 29, so as to control the mode oflaser generation (e.g., generation of a vertical line, a horizontalline, a vertical center line, a vertical 90° line, etc.), and to effectON/OFF control of the electric power supply.

One example of the receiver 5 is shown in FIG. 9, which may be suitablyused in combination with the laser emitter having the abovementionedstructure.

In the receiver as shown in FIG. 9, key switches 32, 33, 34, 35 are usedto perform a remote control of the laser emitter 1. Thus, for example,the key switch 32 is assigned to the generation of a vertical line, thekey switch 33 is assigned to the generation of a horizontal line, thekey switch 34 is assigned to the generation of vertical and horizontallines, and the key switch 35 is assigned to the ON/OFF control of theelectric power supply.

The rotation mechanism 2 has a structure that is basically the same asthat shown in FIG. 4, except the additional provision of the laser beamemission for marking the floor surface.

Although infrared ray is suitably used as the communication signal fordriving the rotation mechanism 2, there may be used anelectromagnetic-type communication signal. The signals to be transmittedand received between the rotation mechanism 2 and the laser emitter 1mat be infrared ray or electromagnetic signal.

The signals for performing a remote control of the driving means for theautomatic coarse rotation ring 2 c and automatic fine rotation ring 2 eof the rotation mechanism 2, i.e., the DC motor unit 8 and the steppingmotor unit 9, are received by the sensors 13 a to 13 d. Therefore, anideal arrangement is that the window openings are provided on the entireperiphery of the rotation mechanism 2 so that the sensors arecircumferentially arranged as tightly as possible, though such anarrangement results in degraded mechanical strength of the casing. Inview of such a potential problem, according to a preferred embodiment ofthe present invention, the side wall of the casing 2 a in its lowerregion has window openings that are spaced from each other at allangular distance of approximately 90°. In this instance, as shown inFIG. 5, the window openings are each provided with at least two sensorswhich are oriented in mutually different directions. In this way, thesignal reception sensitivity can be improved without degrading themechanical strength of the casing 2 a.

When the rotation of the laser emitter by the rotation mechanism isstopped, particularly in the case of a sensor-type laser emitter, theremay be instances wherein the degree of horizontal or vertical alignmentof the laser line is still being controlled. Therefor, in considerationof such a situation, it is preferred that the operation of the rotationmechanism is stopped with a time lag of at least 3 seconds after therotation of the laser emitter has been stopped, so as to realize aprecise positioning.

FIG. 10 is a perspective view showing the detail of the stepping motorunit 9 in the rotation mechanism according to the present invention,wherein reference numeral 9 a denotes a stepping motor, and referencenumeral 9 b denotes a power transmission mechanism.

the power transmission mechanism 9 b includes a guide pin 9 b ₁ integralwith, and projecting from the outer periphery of the automatic finerotation ring 2 d, a guide member 9 b ₂ having catch portions c engagedwith the guide pin 9 b ₁ from both sides in a direction indicated by thedouble arrow, in which the automatic fine rotation ring 2 d is rotated,a screw rod 9 b ₃ rotatably supported by bearings (not shown) forholding the guide member 9 b ₂ in a threaded engagement therewith, andadapted to be rotated by the stepping motor 9 a to cause a slidingmovement of the guide member back and forth along the longitudinal axisof the screw rod 9 b ₃, and a pair of interrupters 9 b _(4R), 9 b _(4L)which are provided for the screw rod 9 b ₃ as being spaced from eachother by a distance M so as to sandwich the guide member 9 b ₂. Thus,the distance M between the interrupters defines a slidable range of theguide member 9 b ₂.

When the stepping motor 9 a is driven to rotate the screw rod 9 b ₃, theguide member 9 b ₂ is caused to slide along the longitudinal axis O ofthe screw rod 9 b ₃. Thus, the automatic fine rotation ring 2 dundergoes a fine movement in a clockwise or counterclockwise direction.In this connection, it is preferred that the range of the fine movementof the ring 2 d is set to the angular range of approximately ±3° (or thedistance of ±2 mm.

In the illustrated embodiment, when the automatic fine rotation ring 2 dis caused to undergo a counterclockwise fine movement, the guide member9 b ₂ slides toward the interrupter 9 b _(4R). As soon as the guidemember 9 b ₂ is detected by the interrupter 9 b _(4R), a signal isgenerated which indicates that the sliding limit in the this directionhas been reached.

On the other hand, when the automatic fine rotation ring 2 d is causedto undergo a clockwise fine movement, the guide member 9 b ₂ slidestoward the interrupter 9 b _(4L). As soon as the guide member 9 b ₂ isdetected by the interrupter 9 b _(4L), a signal is generated whichindicates that the sliding limit in this direction has been reached.

In the rotation mechanism including the power transmission mechanism 9 bof the structure as explained above, during the course of positioningwherein the laser line L is to be aligned with the convergent point ofthe light reception sensor portion of the receiver 5 by rotating theautomatic fine rotation ring 2 d in a clockwise manner, for example, arecovery control is performed when the laser line L has passed theconvergent point of the light reception sensor portion. In thisconnection, it is assumed that there definitely exists a particularlocation within the sliding range M of the guide member 9 b ₂, where thelaser line L coincides with the convergent point of the light receptionsensor portion of the receiver 5.

First of all, when the laser line L passes over the convergent point andthe guide member 9 b ₂ continues to slide toward the interrupter 9 b_(4L) and is detected thereby, a signal is generated to indicate thatthe guide member 9 b ₂ has reached its sliding limit.

Then, the stepping motor 9 a is driven in the reverse direction to causea counterclockwise rotation of the automatic fine rotation ring 2 d byan angular amount of 3° (corresponding to the center of the distance M).The DC motor 8 a is also driven to cause a clockwise rotation of therotation ring 2 c by an angular amount of 6°. Then, a counterclockwiserotation of the automatic fine rotation ring 2 d is caused by thestepping motor 9 a so that the laser line L comes into alignment withthe convergent point.

In the process of the abovementioned repositioning, if the laser linepasses over the convergent point without being aligned therewith, theguide member 9 b ₂ continues to slide toward the interrupter 9 b _(4R)and is detected thereby, so that a signal is generated to indicate thatthe guide member 9 b ₂ has reached its sliding limit. Based on thissignal, the stepping motor 9 a is driven in the reverse direction tocause a clockwise rotation of the automatic fine rotation ring 2 d by anangular amount of 3° (corresponding to the center of the distance M).The DC motor 8 a is also driven to cause a counterclockwise rotation ofthe rotation ring 2 c by an angular amount of 6°. Then, a clockwiserotation of the automatic fine rotation ring 2 d is caused by thestepping motor 9 a so that the laser line L comes into alignment withthe convergent point.

In the rotation mechanism wherein an automatic tracking control isperformed as explained above, a similar recovery control is repeatedlyperformed for the automatic coarse rotation ring 2 c and the automaticfine rotation ring 2 e until the laser line L is aligned with theconvergent point. When the guide member 9 b ₂ is detected by theinterrupters 9 b _(4R), 9 b _(4L), the automatic coarse rotation ring 2c and the automatic fine rotation ring 2 e are operated in accordancewith the time charts as shown in FIGS. 11( a) and 11(b).

In connection with the abovementioned recovery control, the position ofthe guide member 9 b ₂ is set substantially to the center of thedistance M by the initial operation performed when the electric powersupply of the rotation mechanism is switched ON. However, the centerposition of the guide member 9 b ₂ is gradually shifted alter thetracking control has been performed for the positioning many times. Therecovery control serves effectively to compensate for such a shifting.

It has been explained above that, upon the recovery control, the angularrange of rotation of the automatic fine rotation ring 2 d is set to ±3°so that this ring is caused to rotate in the reverse direction by anamount of approximately 3° (i.e., ten thousands steps of the steppingmotor 9 a). However, the present invention is not limited to such aspecific example, and the angular range may be set to another suitablerange.

It has also been explained above that, upon the recovery control, theautomatic coarse rotation ring 2 c is rotated by an angle of 6°, thoughthe present invention is not limited to such a specific angular range.The rotation angle of 6° corresponds to the operation time of the DCmotor for approximately 0.33 sec. By causing the automatic fine rotationring 2 d to rotate in the reverse direction, and subsequently causingthe automatic coarse rotation ring 2 c to rotate in the directionopposite to the automatic fine rotation ring 2 d, it is possible toresume the initial state of the laser line positioning.

FIG. 12 is a schematic view showing the detail of the interrupters 9 b_(4R), 9 b _(4L). These interrupters 9 b _(4R), 9 b _(4L) aretransmission-type photo-interrupters wherein a light emitting diode anda light receiving element are arranged opposite to each other in thehousing, for performing a non-contact detection of the change in lightintensity on the side of the light receiving element, which arises froman object passing therethrough, in order to detect the sliding limit ofthe guide member 9 b ₂.

According to the present invention, instead of the interrupters as shownin FIG. 12, there may be used a reflection-type interrupters such asthat shown in FIG. 13. There is no particular limitation to the type ofthe interrupters.

INDUSTRIAL APPLICABILITY

According to the present invention, there is provided a rotationmechanism, which allows a rapid and accurate focusing of the laser lineemitted from the laser emitter, and which is compact in structure.

1. A rotation mechanism for mounting and rotatably supporting a laseremitter thereon, said rotary mechanism comprising: a casing including abottom wall and a side wall connected to the bottom wall, said casingdefining therein a receiving space; and a plurality of rotation ringsthat are arranged layered with each other in the receiving space of thecasing; said plurality of rotation rings comprising: an uppermostrotation ring in the form of a manual coarse rotation ring that isdirectly connected to the laser emitter so as to support the laseremitter, the manual coarse rotation ring operable to manually rotatingthe laser emitter to achieve a coarse angular positioning thereof; anautomatic coarse rotation ring operable to rotate the laser emitter at arelatively high speed together with another of the plurality of rotationrings which is layered immediately above the automatic coarse rotationring, the automatic coarse rotation ring having a first driving meansarranged on another of the plurality of rotation rings which is layeredimmediately below the automatic coarse rotation ring; a manual finerotation ring operable to slightly rotate the laser emitter manuallytogether with another of the plurality of rotation rings which islayered immediately above the manual fine rotation ring; and anautomatic fine rotation ring for rotating the laser emitter at arelatively low speed, together with another of the plurality of rotationrings which is layered immediately above the automatic fine rotationring, the automatic fine rotation ring having a second driving meansarranged on another of the plurality of rotation rings which is layeredimmediately below the automatic fine rotation ring; wherein the manualcoarse rotation ring, the automatic coarse rotation ring, the manualfine rotation ring, and the automatic fine rotation ring are coaxiallydisposed in the receiving space defined by the casing.
 2. The rotationmechanism according to claim 1, wherein the driving means for theautomatic coarse rotation ring comprises a DC motor for allowing a highspeed rotation, and the driving means for the automatic fine rotationring comprises a stepping motor for allowing a low speed rotation. 3.The rotation mechanism according to claim 1, wherein the side wall ofthe casing has window openings that are spaced from each other at anangular distance of approximately 90°, and wherein the window openingsare each provided with at least two sensors adapted to receive controlsignals for the driving means of the automatic coarse rotation ring andthe driving means of the automatic fine rotation ring, the at least twosensors of each window opening being oriented in mutually differentdirections.
 4. The rotation mechanism according to claim 1, furthercomprising monitoring means for completing an operation of the rotationmechanism with a time lag of at least three seconds after a positioningof the laser line has been completed.
 5. The rotation mechanismaccording to claim 1, further comprising power transmission meansarranged between the automatic fine rotation ring and the driving meansthereof, the power transmission means comprising: a guide pin integralwith, and projecting from an outer periphery of the automatic finerotation ring; a guide member having catch portions engaged with theguide pin from both sides in a direction in which the automatic finerotation ring is rotated; a screw rod holding the guide member, thescrew rod threadably engaged with the guide member and adapted to berotated by the driving means so as to cause a sliding movement of theguide member back and forth along the longitudinal axis of the screwrod; and a pair of interrupters positioned at limits of the slidingmovement of the guide member back and forth along the longitudinal axisof the screw rod, the pair of interrupters operable to perform arecovery control by detecting forward and rearward sliding limits of theguide member and causing, when it has been detected that the slidinglimit has been reached, the automatic fine rotation ring and theautomatic coarse rotation ring to be rotated in a clockwise orcounterclockwise manner whenever necessary, so as to position the laserline with a convergent point.
 6. The rotation mechanism according toclaim 1, a shaft extending through the manual coarse rotation ring,through the automatic coarse rotation ring, through the manual finerotation ring, and through the automatic fine rotation ring.
 7. Therotation mechanism according to claim 6, wherein the shaft integral withthe bottom wall of the casing.
 8. The rotation mechanism according toclaim 1, wherein the plurality of rotation rings are layered with theautomatic coarse rotation ring underlying the manual coarse rotationring, with the automatic fine rotation ring underlying the automaticcoarse rotation ring, and the manual fine rotation ring underlying theautomatic fine rotation ring.
 9. A rotation mechanism for mounting androtatably supporting a laser emitter thereon, said rotary mechanismcomprising: a casing including a bottom wall and a side wall connectedto the bottom wall, said casing defining therein a receiving space; anda plurality of rotation rings that are arranged layered with each otherin the receiving space of the casing, the plurality of rotation ringscomprising: a manual coarse rotation ring directly connected to thelaser emitter so as to support the laser emitter, positioned uppermostof the plurality of rotation rings, and manually operable to rotate thelaser emitter to achieve a coarse angular positioning of the laseremitter; an automatic coarse rotation ring layered immediately below themanual coarse rotation ring such that rotation of the automatic coarserotation ring rotates rotate the laser emitter together with the manualcoarse rotation ring; an automatic fine rotation ring layeredimmediately below the automatic coarse rotation ring such that rotationof the automatic fine rotation ring rotates the laser emitter togetherwith the manual coarse rotation ring and the automatic coarse rotationring; and a manual fine rotation ring layered immediately below theautomatic fine rotation ring and manually operable to slightly rotatethe laser emitter together with the manual coarse rotation ring, theautomatic coarse rotation ring, and the automatic fine rotation ring; afirst driving means positioned on the automatic fine rotation ring, thefirst driving means operable to rotate the automatic coarse rotationring; and a second driving means positioned on the manual fine rotationring, the second driving means operable to rotate the automatic finerotation ring; wherein the manual coarse rotation ring, the automaticcoarse rotation ring, the manual fine rotation ring, and the automaticfine rotation ring are coaxially disposed in the receiving space definedby the casing.